Re: More efficient way to exclude footers

EDIT:

Well I feel silly. As AnomalousMonk below mentioned, I had (unintentionally) provided the same solution as Athanasius did earlier. I could have sworn Athanasius' solution involved reading in the file all into an array before processing. That is what I get for not reading all the replies carefully I suppose.

Original reply spoilr'd to avoid polluting the thread with redundant bits (Unless there is a "Delete Post" gubbin I somehow missed?)

Just to build off what ikegami mentioned earlier.

Here is a way to use a sliding window/rolling buffer to process the file and skip the required lines if the file is too large to be read into memory all at once:

#!/usr/bin/perl
use 5.018;
use strict;
use warnings;

my $header_lines = $ARGV[0] // 0;
my $footer_lines = $ARGV[1] // 0;

# skip header
<DATA> for 1 .. $header_lines;

# print everything but the footer lines
my @buffer;
while ( my $line = <DATA> ) {
    chomp $line;
    push @buffer, $line;
    
    say shift @buffer if scalar @buffer > $footer_lines;
}

__DATA__
header 01
header 02
line 01
line 02
line 03
line 04
line 05
footer 01
footer 02
footer 03
[download]

Output:

blingy > buffer.pl 2 3
line 01
line 02
line 03
line 04
line 05

blingy > buffer.pl 1 1
header 02
line 01
line 02
line 03
line 04
line 05
footer 01
footer 02

blingy > buffer.pl 2
line 01
line 02
line 03
line 04
line 05
footer 01
footer 02
footer 03

blingy > buffer.pl 0 3
header 01
header 02
line 01
line 02
line 03
line 04
line 05

blingy > buffer.pl
header 01
header 02
line 01
line 02
line 03
line 04
line 05
footer 01
footer 02
footer 03
[download]

Comment on Re: More efficient way to exclude footers Select or Download Code

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Re^2: More efficient way to exclude footers by AnomalousMonk (Archbishop) on Aug 19, 2015 at 21:48 UTC
Again, isn't this essentially what Athanasius already suggested here? Give a man a fish: `<%-{-{-{-<`	[reply] [d/l]
Re^3: More efficient way to exclude footers by ateague (Monk) on Aug 19, 2015 at 22:09 UTC
Ach! You are absolutely right. I have updated the original post	[reply]